No, you've got that completely wrong, Bill. I'm not saying it's not warming nor am I saying we're not contributing to the warming. I'm asking a basic scientific question: Of the total climate change, what is mankind's contribution to it (expressed as a percentage or ratio)?

There is no such thing as climate "balance" or "stasis." It's continually in a state of change. So, are we speeding up the change or slowing it down, and if so, by how much?

The best estimate, Sean, is that humans are responsible for slightly more than 100% of current warming, because a number of the natural climate forcings are currently negative. In other words, without us, it would be getting colder now.

Regardless of the scientific veracity, that's going to be a hard sell for the alarmists, Bill. In effect it's tantamount to a claim that humans are responsible for any and all climate change, that our activity is a more dominant force than the sun, than plate tectonics, than orbital forcing, than the solar system's position within the galaxy, etc., etc. I mean, the alarmists were already having a tough time selling the concept of mankind's contribution to climate change, let alone identifying mankind as the dominant force driving it.

Further, to describe these other forces (solar, orbital, etc.) as a "myth," while claiming that the climate tends toward stability unless acted upon by an external force, flies in the face of several scientific fields. Solar, gravitational and orbital forces alone would preclude anything that could be described as "stable." Now add in moving land masses, the position of mountain ranges and high/low pressure areas, the distribution of oceans relative to the equator, tidal forces, daily and seasonal heating/cooling cycles, and of course what we know of past climate cycles from fossil and ice core records, you'd have to have a wildly exotic definition of the term "stable" before you could apply it to planetary climate.

I'd say "good luck with that," but it will take a lot more than luck. I think it will take a mass cerebral meltdown of Australian proportions before the rest of the planet's inhabitants buy it.

Sean, I think you've summarized it all well. In the 4.6 billion years or so that our planet has been around, the climate has been characterized by vast extremes, at least relative to what we've seen in modern times. The past few centuries have been hospitable to human social and technological advancement, but I never would suppose that this would be likely to extend into the indefinite future.

While I've been putting Bill through his paces, I do believe that there has to be some human contribution to climate, probably large enough to be discernible and perhaps predictable (though I'm not fully convinced of the latter, given our less than stellar record in predicting the natural evolution of large systems in nature). However, I also believe that those who wish to advance widespread acceptance of the notion of anthropogenic climate change have, in their zeal, compromised their objectivity, often to the point that it undermines the credulity of their arguments.

Why the change in terminology from "global warming" to "climate change"?

Lore has it that political strategist Frank Luntz pushed this terminology because it sounded less threatening (see Luntz Memo (PDF)). However, both of the terms in question are used frequently in the scientific literature, because they refer to two different physical phenomena. As the name suggests, 'global warming' refers to the long-term trend of a rising average global temperature. 'Climate change', again as the name suggests, refers to the changes in the global climate which result from the increasing average global temperature. For example, changes in precipitation patterns, increased prevalence of droughts, heat waves, and other extreme weather, etc.

"In the thirty years leading up to the 1970s, available temperature recordings suggested that there was a cooling trend. As a result some scientists suggested that the current inter-glacial period could rapidly draw to a close, which might result in the Earth plunging into a new ice age over the next few centuries.

I guess this time they've got it right though huh? No chance they'd be wrong twice eh? That whole local phenomenon or multi-decade counter-trends couldn't possibly be in effect now could it? I guess there was some remedial science education occurring since the 1970s when they misinterpreted that local, half-the-planet, multi-decade cooling trend to be signs of an impending ice-age.

Whew, I'm glad they figured it out before we squandered cash & country trying to prevent the cooling and we're not being led astray twice in one lifetime! It could have been tragic - having bankrupted the western world preventing the ice age that wasn't coming and not leaving anything left to fight the warming that was the real problem.

You'll note that in the 1970s, there were contradictory analyses. The temperature records have gotten much better since then, and they ALL show warming. Not to mention all the other evidence of warming around the globe: melting polar ice, rising sea level, plants blooming earlier, etc.

As to the costs, a number of studies have shown that the cost of failing to address climate change will be far higher than the cost of addressing it. We can pay now, or we can pay a lot more later.

The best estimate, Sean, is that humans are responsible for slightly more than 100% of current warming, because a number of the natural climate forcings are currently negative. In other words, without us, it would be getting colder now.

Regardless of the scientific veracity, that's going to be a hard sell for the alarmists, Bill. In effect it's tantamount to a claim that humans are responsible for any and all climate change, that our activity is a more dominant force than the sun, than plate tectonics, than orbital forcing, than the solar system's position within the galaxy, etc., etc. I mean, the alarmists were already having a tough time selling the concept of mankind's contribution to climate change, let alone identifying mankind as the dominant force driving it.

Further, to describe these other forces (solar, orbital, etc.) as a "myth," while claiming that the climate tends toward stability unless acted upon by an external force, flies in the face of several scientific fields. Solar, gravitational and orbital forces alone would preclude anything that could be described as "stable." Now add in moving land masses, the position of mountain ranges and high/low pressure areas, the distribution of oceans relative to the equator, tidal forces, daily and seasonal heating/cooling cycles, and of course what we know of past climate cycles from fossil and ice core records, you'd have to have a wildly exotic definition of the term "stable" before you could apply it to planetary climate.

I'd say "good luck with that," but it will take a lot more than luck. I think it will take a mass cerebral meltdown of Australian proportions before the rest of the planet's inhabitants buy it.

Sean, nobody is describing those other forces as "myths". We've measured them, we understand them, and they're just not having a significant effect at the present time. For example, solar output has gone down while the Earth's temperature has gone up. Why is it that so many people who deny the reality of global warming assume that scientists grabbed onto CO2 as the boogie man, put on the their blinders and ignored all other possible sources? Nothing could be further from the truth. See It's a Natural Cycle., the summary of which is "A natural cycle requires a forcing, and no known forcing exists that fits the fingerprints of observed warming - except anthropogenic greenhouse gases," and CO2 is Not the Only Driver of Climate, the summary of which is "Theory, models and direct measurement confirm CO2 is currently the main driver of climate change."

And compared to what's happening now, our climate has been very stable for a very long time, in fact for nearly all of human existence. The changes we're causing are happening far more quickly than any past climate change we've been able to detect.

Sean, nobody is describing those other forces as "myths". We've measured them, we understand them, and they're just not having a significant effect at the present time. For example, solar output has gone down while the Earth's temperature has gone up. Why is it that so many people who deny the reality of global warming assume that scientists grabbed onto CO2 as the boogie man, put on the their blinders and ignored all other possible sources? Nothing could be further from the truth. See It's a Natural Cycle., the summary of which is "A natural cycle requires a forcing, and no known forcing exists that fits the fingerprints of observed warming - except anthropogenic greenhouse gases," and CO2 is Not the Only Driver of Climate, the summary of which is "Theory, models and direct measurement confirm CO2 is currently the main driver of climate change."

And compared to what's happening now, our climate has been very stable for a very long time, in fact for nearly all of human existence. The changes we're causing are happening far more quickly than any past climate change we've been able to detect.

Yeah, they pretty much are describing those other forces as myths. On the "Comprehensive Review" page you linked, there is a sidebar titled "Most Used Climate Myths," which lists, "Climate's changed before," "It's the sun," etc., as myths.

As for stability, yes, we (as in modern humans) are in the midst of a nearly unprecedented period of climate stability. Do you really think that's going to last forever, whether we're here or not? From purely an odds perspective, it would seem like we're due for some instability. That's a far cry from saying we're actively bringing it on. As for it being that stable for most of human existence, no, I don't think that's the case. I mean, our not-too-distant ancestors were once able to walk from Asia to North America...